Relaxin-2 is a naturally occurring peptide hormone that belongs to the insulin family (Schwabe and McDonald 1977; Rinderknecht and Humbel 1978) and can be isolated from human blood fluid (Wilkinson and Bathgate 2007). However, this would mean an enormous expenditure, not providing the desired and required yields, and in addition, it would be difficult to provide the material in a comparable quality and purity.